This invention relates to a wye-shaped dual backflow check valve for a vacuum sewage system and a vacuum sewage system incorporating the wye-shaped dual backflow check valve.
Check valves are often used in plumbing and piping systems to block the flow of fluid in a particular direction. Specifically, backflow check valves are designed for installation in a sewer pipe to allow sewage to pass downstream through the main line while preventing water and sewer gases from traveling upstream into another line, i.e. to prevent backflow or backsurge. Backflow check valves have been used in vacuum sewage systems such as the sewage systems disclosed in U.S. Pat. No. 4,373,838. Typically, check valves in known vacuum sewage systems are installed entirely in the service lines which feed into a branch line(s). These service lines generally flow upwardly to branch lines in the vacuum system, so check valves are installed in the service lines to prevent back surge into the service line. However, check valves are restricted in use in these systems because they frequently require maintenance. While the prior art check valves prevent backflow into the service line, backflow into the branch line is not prevented when fluid flows downstream from the service line. As a result of this problem, backflow or back surge of up to 20% of the transported fluids has been observed in the branch line. This is a significant problem because a line that becomes filled with liquid in a vacuum sewage system may fail to operate due to excessive pressure loss (i.e., may become xe2x80x9cwaterloggedxe2x80x9d).
The present invention relates to a wye-shaped check valve installed in a vacuum sewage system, wherein the check valve prevents backflow of sewage into the service line and the branch line. This is significant in that it not only prevents the possibility of filling a service line or a branch line with liquid, but also increases the operating efficiency of the system because all relevant force is applied in the proper direction of flow. Thus, sewage will be conveyed a further distance towards a disposal station with one valve (evacuation) cycle. In addition to the above-described advantages, the wye-shaped dual check valve of the present invention permits vacuum system service lines to be connected to branch lines in substantially the same horizontal plane. This provides a significant advantage because better overall drainage efficiency of the system is obtained by incorporating as few profile changes in the sewage transport lines as possible, thus allowing the fluid flow to experience as few dynamic flow changes as possible.
These and other problems are eliminated by the present invention which provides for a wye-shaped dual backflow check valve in a vacuum sewage system.
In one embodiment of the present invention, the dual backflow check valve used in a vacuum sewage system has a valve body including a primary (branch) conduit with an upstream and a downstream portion and a secondary (service) conduit; and a valve flap hinged at the junction between the primary conduit and the secondary conduit such that the valve flap can prevent flow into the upstream portion of the primary conduit or into the secondary conduit. In another embodiment of the present invention, the upstream portion of the primary conduit forms a primary valve seat and the secondary conduit forms a secondary valve seat, wherein the valve flap can sealingly engage either the upstream portion of the primary conduit or the secondary conduit. Yet another embodiment of the present invention includes a rubber gasket on both the primary valve seat and the secondary valve seat. In another embodiment of the present invention, the primary conduit and the secondary conduit are oriented on a substantially horizontal plane. In still another embodiment of the present invention, the primary valve seat and the secondary valve seat are slightly angled in a direction from the valve flap hinge and toward the downstream portion of the primary conduit. In another embodiment, the upstream portion of the primary conduit and the secondary conduit form an acute angle of approximately forty five degrees.
It is therefore a primary object of the present invention to provide a dual backflow check valve used in a vacuum sewage system wherein the dual check valve can prevent backflow into either the primary (branch) line or the secondary (service) line of the vacuum sewage system.
Another important object of the present invention is to provide a dual backflow check valve which operates efficiently when both the primary conduit and the secondary conduit are oriented on a substantially horizontal plane.
It is also an important object of the present invention to provide a dual backflow check valve which allows the primary (branch) line of the drainage system to be buried at a shallower depth than necessary with the prior art, thereby significantly decreasing the costs associated with designing and installing a drainage system.
Another object of the present invention is to provide a dual backflow check valve which includes fewer profile changes than the prior art, thus allowing the design of a drainage system of greater efficiency because of increased rates of fluid flow and/or decreased probability of xe2x80x9cwaterloggingxe2x80x9d (i.e., excessive pressure loss).
Additional objects and advantages of the present invention will become apparent and a more thorough and comprehensive understanding may be had from the following description taken in conjunction with the accompanying drawings forming a part of this specification.